An Overview on Ionic Bond

A type of chemical bond formation that involves the electrostatic attraction between opposite charges, or between two atoms with vastly different electronegativities, is known as ionic bonding. Ionic bonding is the primary interaction that occurs in ionic compounds, and it is the most common type of chemical bonding found in the environment. It is one of the most common types of bonding, along with covalent bonding and metallic bonding, and it is used in many applications. Ions are atoms (or groups of atoms) that have an electrostatic charge on their surface or in their surroundings. Atoms that gain electrons form ions that are negatively charged (called anions). When atoms lose their electrons, they form positively charged ions (called cations). Electrovalence is the term used to describe this transfer of electrons, as opposed to covalence. However, while the cation is typically a metal and the anion is typically a nonmetal, these ions can be more complex in nature, such as molecular ions like NH₄⁺ or SO₄^2- in the most basic of cases. A simple explanation is that an ionic bond is formed when electrons are transferred from a metal to a non-metal in order to achieve a full valence shell for both atoms in the bond.

Ionic compounds conduct electricity when they are molten or in solution, but they do not conduct electricity when they are solid. Ionic compounds typically have a high melting point, which varies depending on the charge of the ions that make up the compound. The higher the charges, the greater the strength of the cohesive forces and the higher the melting point of the metal. Aside from that, they have a tendency to be soluble in water, with the stronger the cohesive forces, the lower the solubility.

Formation of Ionic Bond

Ionic bonding can occur as a result of a redox reaction in which atoms of an element (typically a metal) with a low ionisation energy give up some of their electrons in order to achieve a stable electron configuration in the presence of another element. This results in the formation of cations. A stable electron configuration can be achieved by accepting one or more electrons from an atom of another element (usually a nonmetal) with greater electron affinity. After accepting electrons, an atom becomes an anion. Most of the time, the stable electron configuration for elements in the s-block and the p-block is one of the noble gases, with specific stable electron configurations for elements in the d-block and f-block being d-block elements. Anions and cations are attracted to one another by electrostatic forces, which results in the formation of a solid with a crystallographic lattice in which the ions are stacked in an alternating pattern of arrangement. Because it is typically impossible to distinguish discrete molecular units in such a lattice, the compounds that are formed are not molecular in nature. In contrast, the ions themselves can be complex, forming molecular ions such as the acetate anion or the ammonium cation, among other things.

For example, Sodium chloride is the chemical formula for table salt. As a result of the reaction between Sodium (Na) and Chlorine (Cl), the sodium atoms each lose an electron, resulting in the formation of cations (Na⁺), and the chlorine atoms each gain an electron, resulting in the formation of anions (Cl). Sodium chloride is formed as a result of the attraction between these ions in a one-to-one ratio (NaCl).

Na + Cl → Na⁺ + Cl^–  →  NaCl

Due to the need for charge neutrality, strict ratios between anions and cations must be maintained. As a result, even though ionic compounds are not molecular compounds, they generally follow the rules of stoichiometry in most cases.

Structure of Ionic Bonding

In the solid state, ionic compounds form lattice structures that are crystalline in nature. Ion relative charges and sizes are the two most important factors that influence the shape of the lattice, and these two factors are interdependent. For example, the formation of the rock salt sodium chloride is also adopted by many alkali halides and binary oxides, such as magnesium oxide, indicating that some structures are universally applicable. Using Pauling’s rules, you can predict and rationalise the crystal structures of ionic crystals with greater accuracy and precision.

Polarisation Power Effect

While the electron cloud of the negative ion in the crystal lattices of pure ionic compounds is spherical in nature, if the positive ion is small and/or highly charged, it will alter the electron cloud of the negative ion, resulting in the distortion described by Fajans’ rules. This polarisation of the negative ion results in the accumulation of extra charge density between the two nuclei, resulting in partial covalency between the two nuclei. Positive ions with charges of 3+ (e.g., Al³⁺) are more easily polarised than smaller negative ions, but this effect is usually only noticeable when large negative ions are involved. In contrast, because of their small sizes, 2+ ions (Be²⁺) and even 1+ ions (Li⁺) exhibit some polarising properties. It is important to note that this is not the same as the ionic polarisation effect, which refers to the displacement of ions in the lattice as a result of the application of an electric field to the system.

Conclusion

A type of chemical bonding that involves the electrostatic force of attraction between oppositely charged ions, or between two or more atoms with sharply different electronegativities, is known as ionic bonding.

Ionic bonding is the primary interaction that occurs in ionic compounds, and it is the most common type of chemical bonding found in the environment. Ionic bonding can occur as a result of a redox reaction in which atoms of an element (typically a metal) with a low ionisation energy give up some of their electrons in order to achieve a stable electron configuration in the presence of another element.

In the solid state, ionic compounds form lattice structures that are crystalline in nature. Ion relative charges and sizes are the two most important factors that influence the shape of the lattice, and these two factors are interdependent. While the electron cloud of the negative ion in the crystal lattices of pure ionic compounds is spherical in nature, if the positive ion is small and/or highly charged, it will alter the electron cloud of the negative ion, resulting in the distortion described by Fajans’ rules.